At the moment, when Galio tries to execute a minion that is at 50% and a minion beside it is lower than the damage of his passive, the nearby minion dies instead and the support item triggers. This mean that if you target a cannon minion with your auto attack and a low caster minion is close to it and has low enough hp, the caster minion is the one that dies and you and your adc gets 14 gold instead of 75. Would it be possible to change the priority or order of the effects so that the support item triggers before the passive?
This is a great point! We talked about it and decided you are right this is a good thing to change. Keep an eye out for sometime in the coming patches hopefully!